The present invention relates to pumps in general, and more particularly to improvements in hydraulic pumps wherein one or more pistons are movable in discrete cylinders of the pump housing to thereby effect the flow of fluid from an inlet port to an outlet port with simultaneous pressurization of the fluid.
It is known to provide the housing of a radial piston pump with several cylinders for discrete pistons which are reciprocable by a rotary member to thereby draw fluid from the inlet port and to pressurize the fluid on its way to the outlet port. As a rule, the pump comprises check valves which are interposed between the cylinders and the outlet port to prevent return flow of pressurized fluid into the cylinders. It is also known to install in such pumps a plurality of valves each of which acts not unlike a flow restrictor and automatically seals the inlet port from the respective cylinder when the pressure of fluid at the outlet port rises to a predetermined value. A drawback of such pumps is that they must be equipped with several flow restrictors which contribute to the initial and maintenance cost of the machine. Moreover, the body of the pump must be formed with an intricate network of channels, bores and similar passages for pressurized fluid in order to enable the valves to react in response to increasing fluid pressure at the outlet port. Still further, such pumps are often associateed or provided with discrete pressure relief valves which prevent excessive rise of fluid pressure at the outlet port. Such pressure relief valves also contribute to the initial and maintenance cost of the pumps.